Figure 3. HLA-C-licensed KIR2DL⁺ NK cells display impaired antiviral activity.

(A) Assessment of HLA-C-mediated licensing of NK cells determined by frequency of CD107a expression and TNF-α production (left panel). Frequency of CD107a⁺ (middle panel) and TNF-α-producing cells (right panel) among different NK-cells subsets (n=12; C2^Hom: n=4; C1^Hom: n=8). (B) Antiviral capacity of NK-cell subsets. KIR2DL1⁺ and KIR2DL3⁺ NK cells were sorted by FACS (left panel). Viral loads in the presence or absence of bulk NK cells (middle panel). Level of NK-cell mediated inhibition of HIV-1 replication exhibited by NK-cell subsets as compared to CD4⁺ T cells alone (right panel). All donors were KIR haplotype A to avoid confounding effects of activating KIR and KIR2DL2 and homozygous for either HLA-C group (C1^hom: n=6, C2^hom: n=2). (A and B) Licensed (2DL⁺ Self) and unlicensed KIR2DL⁺ NK cells (2DL⁺ Nonself) are defined by the expression of KIR2DL1 and KIR2DL3 and the donor HLA-C haplotype (2DL⁺ Self: C2^Hom: KIR2DL1⁺/L3⁽⁻⁾, C1^Hom: KIR2DL3⁺/L1⁽⁻⁾; 2DL⁺ Nonself: C2^Hom: KIR2DL1⁽⁻⁾/L3⁽⁺⁾; C1^Hom: KIR2DL3⁽⁻⁾/L1⁽⁺⁾). Bulk and KIR2DL1⁽⁻⁾/L3⁽⁻⁾ NK cells (2DL⁽⁻⁾) served as internal controls. (C) Antiviral capacity of bulk NK cells in the presence or absence of KIR2DL antibodies (left panel; n=17: C1^Hom: n=5, C1/C2: n=9, C2^Hom: n=3). Viral loads in the presence or absence of NK cells (middle panel) or in the presence of KIR antibodies that do (α2DL Self) or do not (α2DL Nonself) bind to donor HLA-C ligands (right panel). α2DL Self indicates addition of α2DL1 to cells from HLA-C2⁺ donors or α2DL3 to cells from HLA-C1⁺ donors; α2DL Nonself indicates addition of α2DL1 to cells from HLA-C1^Hom donors or α2DL3 to cells from HLA-C2^Hom donors. Black bars represent the median. Statistical analyses: Wilcoxon matched-pairs signed rank test. See also Figure S2 and S3.